Electron beam control apparatus



Dec. 6, 1949 E. D. GOODALE ET AL 2,490,731

ELECTRON BEAM CONTROL APPARATUS Filed Feb. 19, 1947 4 Sheecs-Sheet l b lNVENTOR OTTO H. SC BY E. D- GO ATTORNEY Dec. 6, 1949 E. D. GOODALE ET AL 4 9 ELECTRON BEAM CONTROL APPARATUS Filed Feb. 19, 194'7 4; sheets sheec 2 INVENTOR OTTO H- SCHADE BY E. n. GOODALE ATTORNEY 1949 E. D. GOODALE ETAL 2,490,731

ELECTRON BEAM CONTROL APPARATUS Filed Feb. 19, 1947 4 Sheets-Sheet 3 INVENTOR OTTO H. SCHADE E D. GOODALE ATTORNFY Dec. 6, 1949 E. n. GOODALE ETAL ELECTRON BEAM CONTROL APPARATUS 4 Sheets-Sheet 4 Filed Feb. 19, 1947 \NVENTORS 0770 H. SCH/10E E. D. GOOD/7L5 B) ATTORNEY Patented Dec. 6, 1949 ELECTRON BEAM CONTROL APPARATUS Elmer D. Goodale, New Rochelle, N. Y., and Otto H. Schade, West Caldwell, N. J., assignors to Radio Corporation of America, a corporation of Delaware Application February 19, 1947, Serial No. 729,421

12 Claims.

This invention in general relates to devices and apparatus for focussing and deflecting an electron beam, and more particularly to such apparatus as is especially adaptable for use in iocussing and deflecting the cathode ray beam in the socalled low velocity beam scanning cathode ray image pick up or camera tubes, such as those known as the orthicon and/ or image orthicon, for instance.

In the television art an optical image to be transmitted is focussed onto a photosensitive mosaic target element of the camera tube to release electrons therefrom, and the quantity of released electrons from each point on the mosaic is representative of the light intensity of that point of the optical image being scanned and which impinges thereon. A cathode ray beam then is moved according to any desired scanning pattern, e. g., in a line by lin manner, over the mosaic and signals are accordingly developed sequentially point by point either by the measurement of the changes in the total charge on the mosaic as the beam traverses it or by the measurement of the efiect of the mosaic charge on the cathode ray beam itself.

In the earlier arrangements of the art to which this invention belongs, it was normal procedure to develop a beam of electrons and to accelerate the speed of the electrons in the beam toward the mosaic to a degree where the electrons, when striking the photosensitive mosaic, struck at a high rate of speed and substantially neutralized the charge on the mosaic. The speed of the electrons upon striking the mosaic was sufficiently great, however, to release secondary electrons from the mosaic and, in some systems, video signals were derived by a collection of the secondary electrons so released. This beam then could be called a so-called hard beam or a stiff beam where th electrons passed through the deflection fields at a relatively high speed. The arrangements suffered from the disadvantage that the efficiency of the scanning tube was not as high as could be desired. Further, there was a tendency on the part of the scansion tube to produce background shading or spurious effects that were not found in the scene being televised, the latter apparently being due to the fact that the speed of the electrons in the beam being great enough to dislodge secondary electrons, these latter electrons, once having been freed, could be attracted to a collector ring or could be attracted back to the positively charged portions of the photosensitive mosaic and thus, by neutralizing at least a portion of the positive charge,

alter the charge distribution from its original or true form so that a shading effect was produced.

There was developed, in the later art, a scansion tube that retained some of the features of the earlier form of camera tube but which had much greater efilciency. This was the socalled orthicon type of tube and. such a tube is shown, for instance, in an article entitled The orthicona television pick up tube by Rose and Iams, published in the RCA Review for October 1939. Another article by the same authors is Television pick up tubes using low velocity electron beam scanning, Proc. I R, E, September 1939. This tube avoids the release of secondary electrons from the photosensitive mosaic due to the action of the electron beam by changing from a high velocity scanning beam to a low velocity scanning beam. A further development of the tube led to the invention of the so-called image orthicon tube, and such a tube is shown, for instance, in U. S. patent application Serial No. 631,441 filed November 28, 1945 by Albert Rose, and in the article by Rose, Weimer, and Law, entitled The image orthicon, Proceedings I R E and Waves and Electrons, July 1946, page 424 et seq.

The image orthicon such as is used at present (one example of which is manufactured by RCA and identified as the RCA-2P23) is very stable in performance at all light levels from several thousand foot-candles to one foot-candle, or less, and has a sensitivity which is in the order of times that of previous pick-up or camera tubes.

The image section of the image orthicon type tube, for instance, contains, among other elements, a semi-transparent photocathode on the inside of the tube end wall, an accelerator electrode, and a target which consists of a thin glass disc with a fine mesh screen very closely spaced to it on the photocathode side. Focussing in the image section is accomplished by means of a magnetic field produced by external coils and by varying the photocathode voltage.

Light from the scene being televised is picked up by an optical lens system and focussed onto the photocathode which emits photoelectrons from each illuminated area in proportion to the intensity of the light striking the area. The photoelectrons released upon the light image being focussed upon the photosensitive cathode are focussed on the target by means of developed magnetic fields which function in conjunction with the tube. Electrostatic accelerating fields move the electrons between the photoelectric other side; by. conductivity through the glass in a time that cathode and the target disc and provide the initial focussing effect.

On striking th target, the released electrons cause secondary electrons to be emitted from the glass target face. The secondary electrons thus emitted are collected by the adjacent mesh screen which is held at a definite potential of about one or several volts relative to the photocathode area. The maximum potential to which the glass disc may rise is therefore limited for all values of light and stabl operation is achieved. Emission of the secondary electrons leaves, on the photocathode side of the glass target, a pattern of positive charges which are representative of the values of light and shade at homologous areas of the scene being televised. The charges thus produced set .up a corresponding potential pattern on the opposite, or scanned side, of the glass target.

The opposite side of the glass target from that onwhich the charges are formed is scanned by a low velocity electron beam produced by the electron gun of the tube. The beam is focussed at the-target by a magnetic field produced by focussing coils positioned externally to the tube, as well as by the electrostatic field produced due to-voltage differences between certain electrodes withinthe tube.

Thereis further provided in the tube a declerating electrode to create a field for decelerating the electrons of the electron beam just prior to their approach to the target. The electrons stop their forward motion at the surface of the glass target. Those electrons not required to neutralizethe charges in the target are then influenced -by the-fields within the tube and are caused to turn back toward the source and then are collected and focussed onto a multi-stage electron multiplier, except when the beam approaches the positively charged portions of the pattern a on theglass target. When the latter condition occurs, the electrons are deposited from the scanning beam-or absorbed from the scanning beam in quantitiesisufficient to neutralize the charge pattern on the glass and this abso-rptively modulated beam is directed back. to the multiplier. Thisdeposition. or absorption leaves the glass with anegative charge pattern on. one side corresponding to the positive charge pattern on the These charges neutralize each other is .lessthan the scanning time of a frame of the picture. transmission.

While this particular type of tube is highly desirable because of its efficiency and sensitivity, it also brings about difficulties that are not present when the high velocity beam type of tube .(e; g., the iconoscope) is used, and these diflicultiesare present because the low velocity electrons in the electron scanning beam are difficult to focus and control.

Forone thing, the electron velocity being comparatively low, a relatively weak electrostatic or electromagnetic field willaffect the beam. Consequently, stray fields have an effect on the beam which-must be eliminated and it is one of the objects of this invention to provide means for focussing and deflecting a cathode ray beam which will be particularly useful for. use with low beam velocity. scanning tubes, but not necessarily limited thereto, and in which the effects of stray. fields from sources external to the tube will beminimize'd or eliminated.

There have been two effects both of, which have caused considerable' difficulty in previously known arrangements. The first of these has been the so-called cross-over efiect in which interaction between the horizontal (line) and vertical (field) deflecting coils due to electrostatic coupling and, possibly to some degree, interaction between the focussing coil and the deflecting coils has produced effects which were highly undesirable. It is anotherof the objects .of this invention, therefore, to provide a deflecting and focussing apparatus which is particularly useful with the so-called low velocity type of scansion tube and in which these mutual interactions will be either eliminated or minimized to a point where they no longer constitute a problem.

In addition to the cross-over effect between the deflecting coils with its consequent results, there has been produced results that were highly undesirable by the electrostatic coupling which exists between the elements within the scansion tube er se and the coils of the apparatus, in particular the horizontal (line frequency) deflecting coil. Various types of known shielding arrangements when used proved unsatisfactory in the elimination both of the cross-over effects and'the efiect caused by the electrostatic couplingbetween the tube elements and the coils; Additionally, therefore, it is another object, and a-major object, of this invention to provide a focussing and deflecting, coil assembly in which these effectswill-be minimized or eliminated.

Still further, it is another of the-objects of this invention to provide an arrangement which is particularly useful and efficient in focussing and deflecting the cathode ray beam in a low scanning speed type of scansion tube;

Among the elements and the arrangements knownto the prior art which contributed to distortion was the arrangement wherein the energizing leads for the deflecting coils were brought out through the inner surfaceof the insulating support for the coils and hence were positioned immediately adjacent the scansion tube itself and this contributed to the coupling between the tube elements and the deflecting coils. Since the current passing through the" deflecting coils is comparatively high in value, the coupling between the coils and the tube elements is sufficient to definitely contribute to distortion. In the arrangement of the present invention; the energizing leads, which supply energy to the deflecting coils, are very short and are shielded over practically their entire length. It is-another-of the objects of this invention to provide an apparatus in which this is d-one'efiicien ly and in which the aforementioned efiects are minimized.

Other and further objects of the inventionwill be apparent from a reading of thehereinafter appended specification.

This invention in general contemplates the provision of a cylindrical focussing coil form comprising a hollow insulating cylinder. Between thecylinder and the focussing coils is a special form of electrostatic shield arrangement which will be explained more fully hereinafter. The main focussing coils are placed about the cylinder and supported thereby and arebroken into three sections mutually separated by insulating rings. At the end of the assembly and positioned most closely to the body of the scanning tube, and by body is meant the section usually referred to as the image section of the tube, two of the sections of the coil are also mutually separated bya mu-metal ring. Energizing of the coilsections is done independently and separately of each other. The ends of the coil support form are terminated in one large ring-like member having a counter-sunk portion. A second ring is provided which fits into the. counter-sunk portion of the first and the edge of the electrostatic shield member is fitted between the two rings in each instance to clamp it firmly.

Wrapped about the upper surface of the coils and spacer rings is, first, a fish-paper Wrapping followed by several layers of audio wire strips wound about the coil form and spaced apart by Waxed lacing twine. Each layer is covered by a wrapping of empire cloth and the entire assembly is wrapped with a winding of acetate cloth electrical tape wrap. Energizing leads are brought out through the various layers and through the top of the assembly to-the outside.

The deflecting coils are supported by an insulating Bakelite hollow cylinder whose outer diameter is less than the inner diameter of the insulating hollow cylinder support for the focussing coils. The form ends in two ring-like metallic members at one end of the coils and a similar pair of members at the extreme end of the form. A special form of shield, as will be described more fully hereinafter, is wound about the form and the edges thereof are held between the rings. Ove r the shield is wrapped a layer of fish-paper. One set of deflecting coils is positioned adjacent this shield and over this set of coils is wrapped a layer of fish-paper wrapping.

On this layer of wrapping is a second shield member similar to the first and clamped between the metallic rings at the end of the form. Over this second shield is wrapped a layer of fish-paper wrapping.

The second set of deflecting coils, which are placed at right angles to the first set of coils, are positioned about this upper layer of fish-paper and on top of the second set of coils is wrapped a single layer of fish-paper covered by a wrapping of acetate cloth electrical tape wrap. Both sets of coils are separated from the metallic clamp rings by an insulating ring spacer.

A third metallic member comprising a hollow re-entrant cylinder flanged at one end is provided, and fastened to it is an insulating strip. Energizing leads for the deflecting coils are brought out through openings bored lengthwise through the solid part of the cylinder wall to terminals on the insulating strip and thus are not only short but are shielded from the focussing coils and particularly from the tube itself. In addition, the

re-entrant section of the cylinder holds the clamping rings which in turn hold the specially formed electrostatic shields, thus grounding these shields to an external framework.

The flanged part of the re-entrant cylinder abuts against the outer surface of an end plate at one end of the focussing coil form, when the deflecting coils as a unit are slipped into the hollow section of the insulating cylinder supporting the focussing coils. This further improves the effective grounding of the electrostatic shields through a low impedance path. A short section of metallic ring having its outer edge out in the form of gear teeth fastens to the outer surface of the ring at the end of the re-entrant cylinder and a hand=operated gear wheel cooperates therei with to turn the deflecting coil assembly relatively to, and independently of, the focussing coil assembly.

In addition, the so-called re-entrant cylinder above mentioned forms a space between its outer wall and the insulating cylinder which acts as a support for the deflecting structure and this space is used to hold an alignment coil. The coil is contained in the space between two cylindrical copper sections and then the edges thereof are connected by a copper strip, this forming an arrangement that resembles a thick copper ring. Fastened to the copper ring is an aluminum backing ring, and between the aluminum and the copper there is placed a brass ring,the outer periphery of which is cut with gear teeth. By means of a hand operated gear, the alignment coil can be moved relative to, and independently of, the other elements of the device.

The hand-operated gear wheels which have been referred to all are mounted in a rack-like member having one portion thereof containing a ring into which there is fitted the neckof the tube with which this apparatus is used. The rack fastens to an end plate at the end of the'focussing coils and the gears mesh with the gear rings on the various parts of the apparatus that have been referred to hereinbefore. This will be clearly seen from inspection of the drawings. While the focussing coil itself remains stationary, the deflecting coils can be moved relatively to the focussing coils and the tube, and the alignment coil can do likewise. Means also are provided for moving the tube relatively to either the deflecting cells, the focussing coil or the alignment coil.

At the end of the focussing coil, opposite to that at which the alignment coil is located and adjacent to the body of the tube used with the apparatus, there is provided a cylindrical memtwo is wound an additional focussing coil which is used with the image orthicon, and the size of the cylinder is such that it may be slipped into and held by the focussing coil assembly, and the end of the unit remote from the flange-like ring abuts against and is fastened securely to the front end plate on the deflecting coil when the cylinder is slipped into the focussing coil assembly. This will be clear from a reference to the figures of the drawings.

Still a further cylindrical member which terminates in a flange-like ring is provided and this member is comprised of insulating material. At the inner end of the cylinder there is fastened a vacuum tube socket to accommodate the upper terminals of the scansion tube, that is the terminals brought out from the body of the tube. Copper strips are led along the inner surface of this cylinder and brought out and connected to terminals on the face of the flange-like or ringlike end of the cylinder and energizing potentials may be furnished to the scansion tube through these terminals, the copper strips being connected at their other end to the tube socket. The cylinder itself is adapted to be slid into the cylinder holding the additional focussing coil until the flange-like end of each of these cylinders abuts each other. On either side of the tube socket there is positioned a mu-metal ring to act as an electromagnetic shield member. A mu-metal or A metal ring is fastened at the end of the additional focussing coil so as to lie between the focussing coil and the deflecting coil assembly 7 and is positioned so as to be substantially in the -herholdingthe. hand. operated gears. .of the-.tube. seatsin thetube socket .whichjhas .beerr referredtobefore and .the pins. comingout oixthe'. .body.of .the tube engage contactz-imthe tnbe:socl etand.through.whichenergizingspotenfliereinbe'fore as being a part. .of. the'rmain focus- ..sing;-coil assembly.

..In its exemplified. form, the tube neck is passed through .the openingin the insulatingcylinder :mentioned immediately hereinbef ore and. passed along throughthe focussingand 'deflectingncoil .and alignment .coil assemblies and thencezthrough .a,.supporting. collar. contained in -.a. bracket. mem- The body tials may be furnished thereto.

.The. invention wilLbest be understood by ref erence to the -drawingsin which:

.Eig.;.1 is a partial ecross-sectional ;view;.of ..,a

..-focussing .and deflecting apparatus constructed in accordance with this invention ;=Fig.; 2 is. a partial cross-sectional viewof .one send portion of Fig. 1;

.Fig. 3 isan exploded perspective-showing the .entire arrangement in accordance :with this invention r Fig.- 4 is a perspective view of-another end-of the..arrangement. in accordance with this inven- ;.tion .and showing supporting apparatus-tor the -;cathode ray tube usedwiththe apparatusand alsodriving "apparatus. for adjusting portions. of

ptheidevice Fig. 5 is a partial showing of one of the shieldv,i'ng means utilized in the inventiomand ;Figs. 6 and 7. are schematic showings of the ad- .ditional focusing. coil and-the mount therefor.

ray .scansion tube.

specificatiomand therehas beendescribed the fact thatthe'tube produces eifectively two low velocity cathode ray beams, oneaof which; is .directed toward a target'at the endof the apparatus and must be focussed thereon,andwhichfurther must be moved sequentially back .and iorth linearlywith respect to the target. in order tom-develop signals representative of the light valuesrcf incremental portions of the optical1image w;hich has been -focussed on the target. The other slowmoving beam is the first beam after .it hasnbeen .turned away from the targetand has beenmodulated in accordance with the charge valuesof the portion of the target to which it hasbeen .-ad-

jacent at any particular time. Further,-it,;h as been brought ,out that the first beam must-be focussed on the target and that the second beam must be focussed on some electrode, which in the exemplary arrangement was thevinput electrode to an electron multiplier unit.

In the illustrated arrangement in .thefigure, for supporting the focussing coil-assembly there has been provided a cylindrical insulating supporting member I9. 'Fastened at each end of this .Sup-

iport is a short metal cylinder ll having the, end

thereof .flanged and having the .cylindricallwrtion' thereof entering the insulating cylindrical shell H1. Contiguous with each of thecylinders II is a flange-like metallic member 12 whichjis partially counter-sunk so that the upper edge of the flange M will fit into the counter-sunk portion' of the flange 12 but may beslightly separated apart from the bottom ofthe. counter-sunk por- 'tion and which, "with" flang -12, forms a clamp.

:Po'sitionedabout, the, outerrface of theinsulating .-:shell:lifl is .a'shieldmember ['3 and:the shieldeis woundtabout the member) so: that it, inritself,

-.comprises. a cylindrical member which isefiec- -.tively flanged and the flanged section thereoflfits 7 between metallic; members II and 7 l2 fiandisin separator rings.

intimate contact with both of these member Thisparticular type ofshield will be shown; here- .-inafter;as Fig. 5.

Positioned about the outer surface of shield memberl-3 is a layer of empire cloth and-next are the focussi-ng'coils which, in this particular invention, comprises four diiierent sectionsof coils-three of which are contained betweenthe .two flange or ring members l2. These coils .are 'wound in accordance with well known electrical theory and need not be described with particu- ..1arity here. They are of the general type known .as magnet coils.

Thethreesections of the focussing coil contained between the flanges I2 are l5, I6, and i? and they are spaced apart from eachother by Coils l5 and it are separated by two Bakelite insulating rings 58 and 59 which themselves are separated apart by a metallic ring .20 comprised of mu-metal or A metal. Coils i6 and I! are separated apart by a single insulating, ring 2|. The coils l5 and H are spaced apart fromand maintained out of contact with ringor flange members I2 by means of Bakelite insulating rings 22 and '23 respectively.

.The advantages of this spacing arrangement and of splitting the focussing coils into three separatesections consists in the fact that stronger iocussing fields are desired at the center of the focussing coil assembly than at the end sections.

.33! forming the coil of a plurality of sections, each .may be may be separately energized and energized todifierent degrees to provide desired gradations .of focussing field strength. This allows a flexibility. of operation that is very desirable. It will Lbe appreciated that the beam, after it is developed, .must befocussed onto the target of the scansion tube accurately and then, after it hasbeen turned .away fromthe target, it must be iocussed again :ontothe multiplier section of the tube.

V This can beaccomplished most accuratelyand most easily :bydividing the focussing coil assembly into a plurality of independent sections which may be .cIJcrgizedinsuch a fashion that focussing is ac- ;complished accurately.

[After the coils i5, i6 and il areplaced on the .xoutcr surface .of shield l3, there is Wound about :the .outer surface of the coils a wrapping 25 of :so-called 'fish paper.

On: top of the fish paper =wrap, there :is a second wrapping 26 which comprises a double layer of empirecloth. Wound about the outer surface of the cloth 26 are a series of so-called audio steel strips 27 and these -arespacedapart by Waxed lacing twine in the {form of strip separators 28. On top of the steel strips- 21 and the separator twine 28 is wounda succession of layers which comprise a wrapping of empire cloth in a single layer'form and betweenthese wrappings are layers of audio steel strips separated by spacing lacing twine as shown.

" In the drawing, there is'illustrated six of such layers which comprise the steel strips separated apartjbythe empirecloth. On top, of the sixth .Jayer and forming a portion of the outer surface of the apparatus there is wound, so as to com- ..pletely cover the space between theinsulating rings- 22 an d.23, a wrapping 3!] of acetate cloth electrical tape.

A second coil form or support of Bakelite or other appropriate insulating material in the form of a hollow cylinder 40 is provided for supporting the unit which constitutes the deflection coil unit. Wound about a portion of the outer surface of the hollow cylinder 40 is a sheet of shielding material 41 which will be described more fully hereinafter in Fig. 5. Around the upper surface of the sheet is wrapped a double wrapping 42 of fish paper. The horizontal deflecting coils 43 then are positioned at the end of the insulating cylinder 49 which is most closely adjacent the body of the scansion tube during operation, and by body is meant that portion of the tube which contains the target member, and also at this end is a metallic cylinder 44 which has the end thereof terminated in a ring or flange-like member 45. The

cylinder 44 must be fastened to the insulating cylinder 49. Positioned adjacent the ring-like member 45 is a second ring-like member 46 which has a counter-sunk section. One edge of the special shielding 4| may be slotted so that it may be folded upwardly and. held between rings 45 and 46 which co-act to form a clamping member. An insulating separator 41 separates the horizontal deflecting coils from the ring 46.

At the edge of the horizontal deflecting coils remote from the ring 41 is a second insulating separator ring 48. Positioned next to the ring 43 is a metallic ring 49 which is countersunk on opposing surfaces. A flanged metallic cylindrical ring 50 is positioned adjacent to and fitting into one of the countersunk portions of ring 49. The other slotted edge of the shield member 4| may be bent upwardly and held together by the rings 49 and 58 which act as a clamp to hold the shield and also to ground the shield since the ring will contact the metallic end section of the focussing coil assembly when it abuts against it. The de flection coils per se may be of the type as illustrated, for instance, in U. S. Patents Nos. 2,155,514 of April 25, 1939, and 2,167,379 of July 25, 1939, both to W. A. Tolson.

Over the horizontal deflection coils 43, there is wrapped a double Wrapping of fish paper 55 and about the outer surface of the fish paper is wound a second special shield member 58 which will be shown more clearly in Fig. 5. Over the shield 56 is wound a single wrapping of fish paper 51. The slotted edges of the special shield 56 may be bent upwardly and one edge may be held between ring 46 and a second ring (not numbered for purposes of clarity of illustration) which co-acts therewith to act as a clamp. The other edge of the shield '56 is similarly held between member 49 and a metallic ring (also not numbered for purposes of clarity) Both of the unnumbered elements are separated from the vertical deflection coils 60. (only a portion of which have been illustrated) by insulating rings. The upper surface of the vertical deflection coils is wrapped with a single wrapping of fish paper and a wrapping of acetate cloth electrical tape 32. The relative positioning of the vertical and horizontal deflection coils is more clearl illustrated hereinafter in Fig. 2.

Positioned in contact with the ring-like edge and. the upper surface of the metallic ring member 59 is a metallic element which may be described as a re entrant hollow cylinder at having a flanged end or that could be described as a short metallic cylinder terminating at each end in a ring like metallic member and in which one of the members is directed downwardly into the hollow cylinder. The shell of the member 55 is bored through lengthwise with several holes and an in- 10 sulating ring-like strip 55 is fastened to the outer surface of the member 55 and has a number of terminals 5? which also may be seen more clearly by reference to Figures 2 and. 4.

The purpose of the member 65 is four-fold. Firstly, the outer ring-like end of the cylinder holds the terminal strip 65 and the energizing leads from both the horizontal and the vertical deflecting coils may be made very short and may be brought out through the holes in the shell to the terminals 61, thus shielding these leads from the focussing coil for the greatest portion of their length and also, to all intents and purposes, eliminating any interaction between the leads themselves and the internal elements of the scansion tube with which this apparatus is associated and which interaction would take place due to electrostatic coupling. Also from a mechanical viewpoint this is highly superior construction over the prior art where the leads were brought up out of the inner surface of the deflecting coil assembly and therefore permitted electrostatic cross-over between their leads and the tube elements. Insertion of the tube and withdrawal thereof from the assembly also produced a certain amount of wear on the insulation of the leads.

Secondly, the ring-like end of the member 65 abuts against the surface of the metal end plate i2 of the focussing coils and in conjunction with members 49 and El} forms a good metallic ground for shields 42 and 55 on the outside of the coil structure as well as limiting the degree to which the coil may be inserted into the hollow cylincler I'll.

Thirdly, the outer surface of the ring or flange in the end of the element 65 which is remote from the deflecting coils supports a toothed ring section which is adapted to co-act with a hand driven gear to turn the whole deflecting assembly relatively both to the focussing coil and to the cathode ray tube with which this apparatus is associated. The co-action of these and other elements for adjustment purposes may be seen more clearly hereinafter in Figures 3 and 4.

Fourthly, the shape of cylinder 65 allows the insertion therein, in the hollow section thereof, of an alignment coil 10 which is contained within the space formed between two hollow metallic cylinders H and l2 and having the end space between them closed. In actual practice, these cylinders have been made of copper and an aluminum backing ring 13 has been provided. This coil has been energized through terminals 14 fastened to insulating terminal strip 15. The edge of metallic ring 16 has been toothed so that a hand operated gear, co-acting therewith, can turn the alignment coil relatively to the cathode ray tube used with this apparatus and such gearing is shown at the point 11. Thus, by means of the gear, the alignment coil can be moved relatively to either the focussing coil or the deflecting coils.

There is normally a bracket-like member which is positioned adjacent the alignment coil and which fastens to an end plate on the end of the focussing coil. For purposes of simplicity, this arrangement has been omitted in Fig. 1 but will be shown clearly in the exploded view of Fig. 3 and in detail in Fig. 4.

The electrostatic shielding between the coils and tube is necessary because high voltages are produced in the deflection coils by the large value currents necessary to drive the coils. The surge voltage from the horizontal coils can produce potentials on the vertical coil sections driving curaieowsr rents of appreciable 'value through them by capacity coupling and thus cause a superposition of horizontal deflection components on"thever"- tical deflection which appears asa vertical oscillation of the deflection lines across the screen. The particular form of shielding used between thedeflection coils eliminates this efi'ect.

A similar condition exists between the deflection coils and the foaming coil and'can produce variations in the focussing current with subsequent periodic defocussing,

A still further reason for the shielding between the'defle'ctioncoil and the tubeis the fact that capacity transfer of someof the surge voltage can inducepotentials'onthe tube leads nearthe socket end of the tube; These potentials appear as superimposed ripples on the output voltage from the tube. The shielding eliminates this effect.

A capacitive coupling ofthe surge voltage produced in the deflection coils towards the front portion of the pick-up tube can similarly produce potentials on the electrostatic elements in this tube portion which may disturb the focussing action in the image section and near the target. The thoroughelectrostatic shielding between the deflection coils and this front'portion of the tube eliminates such effects; n

One other important shielding is produced by the fact that the alignment coil 7!! is encased in a heavy copper form. This is done for thereason that this coil'will otherwise pick up portions of the deflecting fields by transformer action which reacts on the deflection of the beam and thus disturbs a normal deflection" by superimcylinder in and goes'" far enough therein to abut and to be securely fastened toth'e end of the deflecting coil assembly. On' theinside oi'the cylinder 89 and near the end there'of which is remote from the focus'sing coil 83 is a metallic ring member SE that is positioned at the end of the cylinder. l itting into the space between this ring and'the end'of the cylinder, and usually; abutting against the clamping elements 45 and 46; is a mu metal ring 84. This mu metal ring usually is coated with an insulating materialand is not grounded.

Next, there is provided an insulating cylindrically shaped member 95 whose end terminates ina flange-like or ring-like insulating'ni'ember 9 I. The outer diameter'of the cyIinder'SU'isS'uch-that it will fit against the inner surface of cylinder Stand may be inserted therein untilthe" member 9'! abuts against the ring 8|. Atthe end of the cylinder 953 which is remote from the ring 9|, and on the inside of the cylinder, there is previded a tube socket 92 which is 'fasten'e'dto', and held by, the insulating cylinder 99. Openings are provided in the tube socket into which the pin members onthe'botto'in of the body of a scansion tube used with this apparatus may be in serted. These openings are fitted with a con ducting material-anda series of coppe'r'strips 93 are provided to act asconductors between these openings and sources of energizing potential exterior to the tube. The copper strips come'out of the front of the cylinder and are bent upwardly where the fasten on the front of the ring 9| to conducting terminal members such as 94. Positioned' a'gainst the tube socket and on the side thereof into which thetube seats is a mu-metal ring 95f;

Referring to Fig. 2, there is shown in partial cross-section a view of" the end of the focussing coil and deflecting coilarrangement at the end thereof which accommodates the alignment coil. The end plate lilll of the fecussing coil is shown with the end ring ofthe cylinder 65 of the defleeting coils being shown as abutted thereagainst. The terminal strip 66, through which energized potentials are fed to the deflecting coils, isshown fastened to the ring member on the end of cylinder 65 and the terminals 6'! are indicated showing the ease with which energizing potentials can be fed to'the deflecting coil. The gear ring illustratedat' the point ll, and by means of which the alignment coil may be adjusted or rotated, is indicated butQdue to the fact that a cross-sectiohal's-howing has been made at the bottom of this'view, the gear segment 8%, by means of which thedeflecting coils are adjusted relatively to the focus's'in'g coil, is not indicated. The insulating cylinderflfi, about which the deflecting coils are wound, isshown partially in cross-section and the relative positioning of the horizontal deflection cells 43; with respectto the vertical deflection coil 66- is indicated. Terminals I05 through which the alignment coil maybe energized are shown.

Referring to" Fig. 3, there is shown an exploded Viewdn perspective of the entire apparatus to show the relative positioning of the various parts whieh have been described hereinbefore with respect to Figure 1,- as well as the relative shapes of these parts. This 'view is for purposes of principles only and no attempthas been made to maintain actual scale relations since the relative size of the elements will depend upon the particular tube with which the apparatus may be used. Inthis view, the'outside wrapping 30 of the focuss'in'g coil is shown and the coil is illustrated asbeing" contained between two aluminors end plates HQ and- Hi. The cylinder 89 having the ring-like members BI and 32 is illustrated with' the additional focussing coil 83 containe'd therebetween. The cylinder will be inserted in the opening furnished by the cylinder on which the focussing coil assembly between two end-plates llllan'd Ill-is wound. The cylinder 8Q w'ill beihserted' into the opening until the ring 82 abuts against the end plate H0. The mumetal ring'flseats into the cylinder 86 and, in the insert'edposition, will abut against the elements GS andAli-and the element of Figure '1.

The insulating cylinder 9!! which ends in a flange-like or'ring-lik'e member 9! is shown as well as the copper strips 93 which run between the tube socket holes and the terminals 9 The'tube socket is seated in the end of the cylinder Slllremote from the ring 9|. The cylinder is inserted in the opening furnished by the cylinder 8!? on which is Wound the additional focussing coil and goes up into the opening until the r'ing9l abuts against the ring 8!. At the other end of the focussing coil that is adjacent the end plate EH, the deflecting coil structure is shown with its tape wrapping 62 and the energizing leads running through openings cut lengthwise in- 13 the wall of cylinder 65. The insulating ring 40, on which these coils are wound, is illustrated and it may be seen how the alignment coil which is included between copper cylinders II and I2 may be slipped over the insulating cylinder 40 and up into the cylinder 65.

In this view, there is shown a bracket member having sides H5 and H6 and a front plate In. The bracket may be fastened to the end plate I I I by means of screws or bolts. In the face of mem ber II'I there is formed a ring-like collar H8 which may be seen more clearly with reference to Figure 4. In practice, the neck of the tube with which this apparatus is associated will'be passed through cylinder 90 and thence through the entire apparatus and through the opening in collar H8 in which it is held. A screw member'is provided for holding the tube neck firmly against the collar. The collar a geared segment H9 which may be turned by hand-operated gear I for turning the tube through a small arc. The gear wheel I2I is provided for engagement with the geared segment on the alignment coil and gear wheel I22 may be engaged with the geared segment on the focussing coil. Adjustments of these structures may be made by means of these hand-operated gears.

Referring to Fig. 4, there is shown, partially broken away, the bracket comprising members H5, H6 and II! along with the collar H8, the latter having an interior in which is seated a cushioning ring I25 of spring bronze. The en-- gagement between gear I22 and gear segment 80 on the deflecting coils is shown as well as the engagement between gear I2I and the gear segment as illustrated at TI on the alignment coil. The relative positioning of the alignment coil with respect to the deflecting coils and the end plate III is shown and the fact that the alignment coil physically goes up partially into the deflecting coil unit is brought out and the position will be such that its correct electrical relationship with the focussing coil is maintained.

Referring to Fig. 5, there is illustrated one of the sheets which form the electrostatic shields which have been referred to hereinbefore in this specification and which have been illustrated as elements I 3, 4| and 56 in Fig. 1 hereinbefore described with particularity in this specification.

The shield has consisted of a so-called kraft paper insulating sheet 530 on both sides of which there is a layer of a conducting material, which, in actual practice, hasbeen a sheet of tin foil. For purposes of convenience of illustration and clarity, there has been illustrated only a portion of the conducting material. The solid lines indicate the conducting material on one side of the sheet and the dotted lines indicate the configuration of the conducting material on the other side of the sheet, after it has been cut in accordance with the present invention. The method of preparing the shield has been as follows:

A very narrow out has been made to remove the tin foil in the long direction of the sheet and this is illustrated at I3I. On the reverse side of the sheet a similar removal has been made along a narrow section and this has been illustrated. at

I32. It should be noted that these two slots do not occur opposite each other in position.

A succession of narrow slots then have been made in the conducting material in a direction cross-wise the sheet and these have been illustrated at I33. 0n the reverse side of the sheet a similar series of slots of conductingmaterial have been cut out of the tin foil and these have 14 been illustrated in the dotted lines as I34. Again, it should be noticed that the slots I33 and the slots I34 are not directly opposite each other on both sides of the sheet, the result being that the slotted sections on one side of the sheet occur in about the center position of the strips of conducting material'on the other side of the sheet. The result is that there are formed on both sides of the sheet a series of strips of conductor which are joined together only at the end thereof near the edges of the sheet. For purposes of illustration and to show the general form of the conducting material, two of these strips have been broken away from the sheet L32 and folded downwardly as illustrated at I25 and I36.

The side edges of the sheet then may be slotted by cutting so that when the bottom edge of the sheet is bent around until it contacts the top edge of the sheet to form a cylinder, the side edges of the sheet may be bent upwardly to a position that is at right angles to the axis of the cylinder so formed. A reference to Fig. 1 will show that this allows the formation of a cylindrical shield which may be held in place by clamping rings such as 45, 46, and 49, 50, thus grounding the shield to the framework of the device and also provides a shield which is very efficient in operation.

The advantage of the slotted arrangement illustrated is that there is no conducting path cross-Wise the sheet for the strips and, similarly, the strips being spaced apart from each other, there is a minimum of conducting path for currents flowing from top to bottom or vice versa in the sheet. 7 Thus, the effects of cross-currents and eddy currents has been cut to an absolute minimum, in addition to the fact that the shield gives a maximum amount of shielding effect. This is a very important consideration in avoiding cross-over effects not only between the deflecting coils themselves but also between the deflecting coils and the focussin coil and the deflecting coils and the tube per se. Additionally, the effects from stray fields in the neighborhood of the device are either entirely eliminated or minimized to a point where they constitute no problem.

For purposes of simplicity and clearness of illustration, there has not been included in Fig. l of this application the electromagnetic shielding means which are utilized to prevent the undesired effects of fringe flux from the end of the deflection coils which is remot from the end adjacent which is positioned mu metal rings 20 and 84'. Inactual practice, a second set of these rings would b utilized and one of the rings would comprise an annular member positioned at or near the end of the deflecting coils which is adjacent the insulating spacer 48 and embracing the outer surface of the insulating cylinder 40. There then would be positioned a second annular member of mu metal or A metal or other highly permeable material embracing the outer surface of the insulatin cylinder I0 about which is positioned the focussing coils and this ring would be normally positioned between two of the iocussing coil sections such, for instance, as I6 and IT and would be located substantially coplanarly with respect to the ring embracing the cylinder 40. This arrangement may be seen with more particularity by referring to the application of Otto H. Schade filed on an even date herewith and entitled Electron beam influencing apparatus.

The purpose of these rings or annular members is to keep the fringe flu'x emanating from the ends of the deflecting coils from affecting the electron multiplier section of the scansion tube with which this apparatus is associated. This is done by providing a low reluctance return path for the flux through the two ringsof magnetic material and through either the audio steel strips or the iron sheath around the apparatus and thence back through mu metal rings 28 and 84 to the deflecting coils themselves. In actual practice, this has resulted in considerable improvement in the results obtainable with the apparatus.

Referring to Fig. 6, there is shown one arrangement which has been used as the additional focussin coil structure. The structure may be formed of a cylindrical metallic member which has at one end thereof a flange-like annular member and at a position intermediate the other end thereof asecond annular ring embracing the outer periphery of the cylinder. The additional fo'cussing coil is wound in the space between these two annular members. The surface of the cylinder is cut away beginning at a positionin the neighborhood of the annular member 82 so as to form two windows through the surface of the cylinder and these windows continue to a position near the end of the cylinder. In one embodiment of this arrangement, the surface of the cylinder is cut away so that two relatively narrow conducting strips, one of which is shown asthe strip I50, extend from the neighborhood of the annular ring 82 to a position near the end cf the cylinder and this leaves the end in the form of a ring of conductin material il. In this end section, the annular ring 85 of Fig. 1 is provided against which the mu metal ring 84 of that figure rests. The windows in the surface of the cylinder 80 then maybe filled by an insulating material such as Bakelite or other well known materials so as to give rigidity to the structure. t

Referring to Fig. '7, there is shown an alternative form of the additional focussing coil support and one which has been very effective in practice. In some respects this may be described as a modification of the arrangement shown in Fig. 6. Instead of having the windows of the structure of Fig. 6 filled with Bakelite or other insulating material, the sections, which in Fig. 6 are the window sections, comprise, in this arrangement, a series of conducting strips which are cut from the surface of the cylinder itself and these conducting strips are shown, for ex-' ample, by the strips I55, I56 and so forth. The end ring I5! of the cylinder has riveted thereto a Bakelite insulating ring I69 to which the ends of the strips such as I55 and I56 are riveted in order to keep these strips firmly in place. This provides a structure in which there are a minimum of conducting paths for the circulation of eddy currents in the structure which would be set up by coupling from the front of the deflecting yoke and which could affect the photosensitive mosaic in the tube with which the apparatus is used. This type of structure has increased by a great number of lines the number of scanning lines that it is possible to develop with the tube used with the structure and where such lines have acceptable resolution. This structure provides, however, a good ground connection from the outer frame of the apparatus, as for instance the members H0 and III, to clamping members 45 and 46 which clamp on of the electrostatic shields and the unnumbered clamping member cooperating with the member 46 and clamping the other electrostatic shield.

It will be appreciated that, if desired, the strip members I55 and I56, for instance, need not all emanate from the section of the cylindrical support 86 which is in the neighborhood of the annular member 82, but could be arranged so that alternate members emanate from the front ring l5i of the structure so that effectively there would be provided a set of strip-like or finger like members which are interleaved.

Having now described the invention, what is claimed and desired to be secured by Letters Patent is the following:

1. An electron beam controlling apparatus comprising means for focussing the electron beam, means for deflecting the electron beam, and at least one electrostatic shield interposed between said fccussing means and said deflecting means comprising a conducting material with a plurality of sets of strips of conducting material, each set having an individual conducting member connected thereto for electrically connecting together the strips forming each set.

2. An apparatus for influencing a cathode ray beam comprising means for focussing said beam, means for deflecting said beam, and at least one electrostatic shield member interposed between said focussing means and said deflecting means, the electrostatic shield member comprising a sheet of insulating material having positioned on either side thereof a sheet of conducting material, the conducting material of each sheet having portions of the conductor removed so as to form a plurality of sets of individual strip-like members each spaced apart from the other strips of the same set and of other sets and having a free end of each strip positioned adjacent a free end of the strips forming another set, at least a por tion of said strips being mutually electrically connected.

3. Apparatus in accordance with claim 2 wherein there is provided in addition conducting frame means positioned outside of the focussing and deflecting means, and means electrically connecting both of said sets of conducting material of the electrostatic shield to the conducting frame.

4. Apparatus in accordance with claim 1 wherein there is provided in addition electromagnetically permeable means positioned so as to at least partially embrace the deflecting means and the focussing means.

5. Apparatus for influencing a cathode ray beam formed within a cathode ray tube comprising an insulating substantially tubular shaped supporting member for accommodating the tube in which said cathode ray beam is formed, means for deflecting the beam in at least one coordinate of movement, means for focussing the beam, said latter means at least partially embracing the deflecting means, electrostatic shielding means positioned between the focussing means and the deflecting means, and electromagnetic means interposed between the deflecting means and the position of the target of the cathode ray tube When in operative position.

6. Apparatus in accordance with claim 5 wherein the means for focussing the cathode ray beam comprise a plurality of individual coils which can be separately excited.

'7. Apparatus for influencing the electron beam formed within a cathode ray tube which has a neck section within which the cathode ray beam is formed and a body section containing a target area comprising a first tubular shaped insulating support by which the neck section of the cathode ray tube may be at least partially embraced, deflecting means supported by said tubular member, a second tubular shaped insulating member having a diameter larger than that of the first tubular member and which is adapted to embrace at least a portion of the first tubular member, means for focussing the cathode ray beam supported by a said second tubular member and comprising a plurality of individual electromagnetic coils, an electromagnetic ring at least partially embracing the second tubular member and positioned between two of the individual focussing coils, a second electromagnetic ring at least partially embracing the first tubular means and positioned between the deflecting means and the body of the cathode ray tube at its operating position, and electrostatic shield means positioned between the focussing means and the deflecting means.

8. Apparatus in accordance with claim 6 wherein there is provided a conducting support means externally of the focussing and deflecting means and wherein the electrostatic shielding means and at least one of the electromagnetic ring means are electrically connected to the conducting support.

9. Apparatus in accordance with claim 7 wherein there is provided in addition electromagnetic conducting means at least partially embracing the focussing means.

10. Means for influencing the cathode ray beam formed within a cathode ray tube having a neck section in which the cathode ray beam is formed and a body section containing a target area comprising a first tubular insulating support, deflecting means positioned about and supported by said tubular means for deflecting the cathode ray beam in at least one coordinate, a second tubular insulating support means having a diameter larger than that of the first insulating support means and into which said first tubular means may be positioned so as to have at least a part thereof embraced by said second tubular means, means supported by said second tubular means for focussing the cathode ray beam, electrostatic shield means interposed between the focussing means and the deflecting means, a third tubular shaped member, a tube socket means contained within said third tubular shaped member, the diameter of the third member being such that it may be positioned within the first and second tubular shaped members so that at least a portion thereof is embraced thereby, a first electromagnetic shielding means comprising a substantially ring shaped member contained within the first tubular member and positioned so as to be interposed between the deflecting means and the body of the cathode ray tube in its operative position, a second electromagnetic shielding means embracing the second tubular member and positioned substantially adjacent the said first ring-like electromagnetic shield, an alignment coil support of substantially tubular shape, an alignment coil held by the alignment coil support, the tubular alignment coil support being of such a diameter as to allow the positioning thereof about the first tubular insulating support member and being at least partially embraced by the second tubular insulating support member, means for moving the first insulating support member relatively to the second insulating support member, and means for moving the alignment coil support relatively to both the first and the second tubular shaped members and independently thereof.

11. A laminated combination electrostatic and electromagnetic shield comprising a sheet of insulating material having a sheet of conducting material positioned on each opposite side surface thereof and wherein each of the sheets of conducting material is slotted to form from each sheet a plurality of individual strips of conducting material lying on each of said opposite side surfaces, adjacent strips on either given surface being separated by said slots and wherein the slots on one surface are coincident and in normal transverse alignment with the strips on the other surface.

12. A laminated combination electrostatic and electromagnetic shield comprising a sheet of insulating material having a sheet of conducting material in contact with each face thereof, said sheets of conducting material having portions thereof removed therefrom to form a surface structure on each face, each of the formed surface structures having a configuration which comprises a supporting strip of conducting material along each of two opposite edges of the sheet face and a series of spaced secondary strips emanating from the supporting strips, each of said secondary strips having a free end, each of said conducting sheets, and the configurations defined thereby, being further so proportioned and the two sheets so oriented relative to one another that slotted areas on one sheet face are transversely projectible normally thereto to fall on areas of conducting material on the other sheet face.

ELMER D. GOODALE. OTTO H. SCHADE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,047,159 Wood et al July 7, 1936 2,172,733 Federmann et a1. Sept. 12, 1939 2,217,409 Hepp Oct. 8, 1940 2,234,998 Worral1 Mar. 18, 1941 2,314,409 Knoop Mar. 23, 1943 2,362,034 Stahl Nov. 7, 1944 

